Stories tagged node


Vibrations create cool patterns

Vibrating surfaces create sound waves. In the video below a plate of metal is vibrated with higher and higher frequencies. Salt spinkled on top of the plate can only stay where the surface is not vibrating. The nonvibrating areas are called nodes. Distance between nodes is shorter for higher frequencies.Standing waves
Standing waves
The patterns you see are known as standing waves. We have an apparatus like this at the Science Museum of Minnesota on the third floor. You might also try to make standing waves in a stretched slinky.

Try doing this yourself

I once stretched rubber from a large balloon over the front of a large car speaker. Using an amplifier and frequency generator, I was able to make similar patterns in salt sprinkled on top of the sheet of rubber. You could try an electric keyboard to produce the different frequencies of sound.

Want to see a longer video?

If you have time here is a link to part 1 of some extraordinary film clips of Hans Jenny experiments from the 1960's and early 70's(28 minutes).